Contrary to what some smokers may hope, antioxidants and other vitamins seem to offer no protection against lung cancer, new research suggests.
In an analysis of eight previous studies, researchers found no evidence that vitamins A, C, E or folate lower a person’s risk of lung cancer.
Across the studies, which followed thousands of adults for up to 16 years, people with the highest intakes of the vitamins were no less likely to develop lung cancer than those with the lowest intakes.
There has been a popular notion that even smokers can ward off lung cancer by taking vitamin supplements, Dr. Eunyoung Cho, the lead author of the new report, told Reuters Health.
“This is not true, and our study confirmed that,” said Cho, an assistant professor of medicine at Harvard Medical School and Brigham and Women’s Hospital in Boston.
She and her colleagues report the findings in the International Journal of Cancer.
Vitamins C and E are antioxidants, which means they help neutralize cell-damaging substances in the body called free radicals. Vitamin A and folate, a B vitamin, also help maintain normal, healthy cells.
All of these vitamins have been hypothesized to cut lung cancer risk, according to Cho’s team, but the research evidence has been spotty. In particular, most prospective studies - those that follow people over time - have found no clear protective effect.
But because these studies have included only a small number of lung cancer cases, their findings are less reliable. So Cho and her colleagues pooled data from eight prospective studies that followed a total of 430,281 adults in Europe and North America, including 3,206 who developed lung cancer.
After the researchers factored in smoking habits and other variables, like overall diet, weight and education, there was no evidence that vitamins A, C, E or folate reduced lung cancer risk.
There was initially some evidence that vitamin C from food, but not supplements, was protective. But that connection disappeared when the researchers accounted for beta-cryptoxanthin, a plant chemical that gives color to oranges, red peppers, carrots and other red-orange fruits and vegetables.
Because many vitamin C-rich foods contain beta-cryptoxanthin, the latter nutrient may help explain the link some studies have found between vitamin C and lower lung cancer risk, the researchers speculate.
In fact, it is still possible that nutrient-rich fruits and vegetables, if not individual vitamins, help protect against lung cancer, Cho said.
These foods, she explained, might confer benefits through components other than vitamins, or through their unique combinations of nutrients - though, she added, there is still much to be learned in this area.
SOURCE: International Journal of Cancer, February 15, 2006.
Revision date: June 22, 2011
Last revised: by Sebastian Scheller, MD, ScD